Feed for fish

ABSTRACT

A fish feed includes carvacrol and/or  salvia  extract (provided that where the fish feed comprises carvacrol and not  salvia  extract the lipid content of the fish feed is at least 15 wt %). The  salvia  extract may be selected from extract of  Salvia officinalis  and extract of  Salvia lavandulifolia . The carvacrol may be synthetic or may be extracted from  Origanum vulgare.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/278,536, filed Oct. 28, 2008, which is the U.S. NationalPhase of PCT/EP2007/050393, filed Jan. 16, 2007, which in turn claimspriority to British application No. 0602426.9, filed Feb. 7, 2006, theentire contents of all the foregoing applications are incorporatedherein by reference.

The present invention relates to a feed for fish, to a method of makingthe feed, to a method of feeding fish with the feed and to fish fed withthe feed.

Fish is an important source of protein for the world's population. It isrecognised that consumption of fish per capita should be increasedbecause of its positive health effects.

However, it is no longer possible to increase the quantity of fishcaught in the wild, because of the effect on fish stocks. Some stocks ofwild fish have collapsed already, and for other stocks the catch must bereduced for the stocks to be sustainable.

Aquaculture (fish farming) is therefore of increasing importance insupplying fish to the world's population.

Fish need protein, fat, minerals and vitamins in order to grow and to bein good health. The diet of carnivorous fish is particularly important.

Originally in the farming of carnivorous fish, whole fish or ground fishwere used to meet the nutritional requirements of the farmed fish.Ground fish mixed with dry raw materials of various kinds, such as fishmeal and starch, was termed soft or semi-moist feed. As farming becameindustrialized, soft or semi-moist feed was replaced by pressed dryfeed. This was itself gradually replaced by extruded dry feed.

Today, extruded feed is nearly universal in the farming of a number offish species such as various types of salmonid, cod, sea bass and seabream.

The dominant protein source in dry feed for fish has been fish meal ofdifferent qualities. Fish meal and fish oil are obtained from so-called“industrial fish”. The catch of industrial fish cannot be increased forthe reasons set out above.

Industrial fish may for example be of North-European origin or ofSouth-American origin, in particular fish caught off the coasts of Peruand Chile. The output of these countries fluctuates somewhat from oneyear to the next. At about 7 year intervals the weather phenomenon ElNiño occurs, and severely reduces the output of industrial fish. Thisaffects the availability of fish meal and fish oil on the world market,and prices rise considerably for these raw materials.

The aquaculture industry and especially the fish feed industry havepredicted for several years that there will be a shortage of both fishmeal and fish oil in the future. Other animal protein sources are alsoused for dry fish feed. Thus, it is known to use blood meal, bone meal,feather meal and other types of meal produced from other slaughterhousewaste, for example chicken meal. These are typically cheaper than fishmeal and fish oil. However, in some geographic regions, such as Europe,there has been a prohibition against using such raw materials in theproduction of feeds for food-producing animals and fish.

It is also known to use vegetable protein such as wheat gluten, maize(corn) gluten, soya protein, lupin meal, pea meal, bean meal, rape meal,sunflower meal and rice flour. Soya is a low price raw material withhigh protein content and is available in very large quantities on aworld-wide basis. Therefore, soya has been used in fish feeds for manyyears.

There is thus pressure to minimise the quantity of raw material used infish feed for aquaculture.

In addition, aquaculture is capital intensive. There are investments incages, pens or ponds, feeding automata, storage facilities and otherinfrastructure. The fish themselves have associated costs as they arepurchased as fingerlings (e.g. trout and salmon species, sea bass, seabream, turbot, halibut, cod) or wild caught (e.g. yellow tail, cod,saithe, tuna species).

The most important single cost in aquaculture is the cost of the feed.Labour costs are also important.

The selling price of the fish and the number of fish that are harvesteddetermine the profitability of the operation.

A faster turnover has several positive results. First, it helps cashflow. Second, it improves risk management. Fish diseases are common, andthe likelihood of an outbreak is higher over a long growing period.There is also a risk that fish will escape due to accidents, e.g. whenshifting nets, or due to bad weather causing wrecked fish pens.

Turnover rate is determined by how fast the fish grow to a harvestablesize. As an example, it takes from 12 to 18 months to raise Atlanticsalmon from smolt (the physiological stage when the Atlantic salmon canfirst be transferred from fresh water to sea water) to harvestable size.Harvestable size is dependent on the fish species and market. Somemarkets for Atlantic salmon prefer fish larger than 6 kg. Rainbow troutis in some markets sold as portion sized and the weight is 300 g.

Growth rate is expressed as percentage increase in body mass from day today (Specific Growth Rate, SGR). This is calculated as:

${SGR} = {\left( {\left( \frac{FinalW}{InitW} \right)^{1/{Days}} - 1} \right) \cdot 100}$

-   -   FinalW=final weight    -   InitW=initial weight    -   Days=time from measuring initial weight to final weight

The SGR does not take into account the amount of feed fed to obtaingrowth. It is a measure of growth rate only. A high SGR is dependent onthe digestibility of the raw materials and how optimal the feedcomposition is with respect to protein and fat ratio, amino acidcomposition and composition of fatty acids. Microingredients such asvitamins and minerals must also be present in sufficient quantities.

Another important economic factor is how efficiently the fish grow onthe feed. Fish growth is in practical terms protein deposition in themuscle (growth of muscle mass).

The common term to describe this is Feed Conversion Ratio (FCR) definedas:FCR=Amount of feed fed (kg)/Net growth of the fish (kg)

FCR varies between fish species and also with the size of the fish. InAtlantic salmon FCR may typically be from 0.7 to 2. Industrial fish feedin the form of pressed feed and extruded feed contains low amounts ofwater, typically from 5 to 10%. The fish body has a much higher watercontent. This explains why the FCR may be lower than 1. An accuratecomparison of the FCR of different feeds should take into account thewater content of the feeds as water does not contribute to growth. Mostprecisely the FCR should be calculated on a dry matter basis. However,as the water content is within a narrow range, and it is cumbersome forthe fish farmer to calculate dry matter FCR, FCR is normally calculatedon the feed including water content.

There is also a distinction between the “biological FCR” and the“economic FCR”. The biological FOR is on the individual fish level. Ittakes account of the actual feed eaten by the individual fish and itsweight gain over the observed period. This is the true performance ofthe feed. As with SGR, biological FCR is a function of the digestibilityof the nutrients, the balance between protein and energy (e.g. fat), thebalance between the different amino acids and the presence of sufficientmicroingredients (such as vitamins and minerals).

In a commercial operation, however, there are numerous individual fishin each pen or pond (e.g. 10000 to 30000 individuals in each pen).Feeding cannot be observed on the individual level. The fish farmer istherefore more concerned about the economic FCR. This is on a cage leveland is defined as the amount of feed fed to the cage and the increase inthe cage's fish biomass over the observation period.

The economic FCR is higher than the biological FCR for several reasons.First, some feed is lost because feed pellets break apart in the feedingsystem and the broken pieces are too small to be eaten or are so smallthat they are recognised as dust. Second, some feed pellets are noteaten by the fish but just sink through the water column. Third, somefeed is lost because the fish are fed to satiation, while feedingcontinues. This is known as overfeeding. Fourth, underfeeding may occur,in which case the FCR increases because a higher proportion of theprotein in the feed will be used for metabolic purposes as opposed tofor muscle deposition. Fifth, fish may escape through holes in the net.The initial biomass is determined by counting the individuals and bydetermining the initial weight by weighing sub-samples of thepopulation. Wrong numbers have an impact on the economic FCR.

Thus, it is desirable to produce a fish feed which leads to good (high)SGR and good (low) biological and/or economic FCR.

To achieve the above objects, additives that can increase thedigestibility of fat and or protein are of value. This can be measuredby the “Apparent Digestibility Coefficient”, calculated as:

${{ADC}(\%)} = {100 - \left( {100 \cdot \left( {\frac{{Yttrium}\mspace{14mu}{in}\mspace{14mu}{diet}}{{Yttrium}\mspace{14mu}{in}\mspace{14mu}{faeces}} \cdot \frac{{Nutrient}\mspace{14mu}{in}\mspace{14mu}{faeces}}{{Nutrient}\mspace{14mu}{in}\mspace{14mu}{diet}}} \right)} \right)}$

Yttrium is added to the diet for the purpose of calculating ADC, but isotherwise not a necessary component of fish feed.

JP2-207758 discloses a low fat fish feed which comprises one or more ofvarious plant essential oils or components extracted therefrom includingcarvacrol. The fish feed is taught to protect fish against infectiousdiseases.

The present inventors have surprisingly found that including in fishfeed either separately or together certain additives which can beextracted from plants or synthesised chemically helps to achieve highSGR and low FCR, thus giving a high fish turnover for a low feed input.

The additives are carvacrol and salvia (sage) extract.

Without wishing to be bound by this theory, the inventors believe thatgrowth of fish is promoted by the additives because digestibility of fatby the fish is improved. It is believed that the two additives havesimilar effects.

Accordingly, in a first aspect, the present invention provides a fishfeed comprising carvacrol and/or salvia extract, provided that where thefish feed comprises carvacrol and not salvia extract the lipid contentof the fish feed is at least 15 wt %.

The term “fish feed” as used herein includes compositions as describedbelow. Typically, fish feed includes fish meal as a component. Suitably,fish feed is in the form of flakes or pellets, for example extrudedpellets.

The term “extract” as used herein includes compositions obtained bysolvent extraction (which are also known as “extracted oils”), steamdistillation (which are also known as “essential oils”) or other methodsknown to the skilled person. Suitable extraction solvents includealcohols such as ethanol.

Preferably, the salvia extract is a concentrate. The term “salvia” asused herein includes plants of the Salvia genus of the Lamiaceae family.Preferred species of salvia are Dalmatian sage (Salvia officinalis) forexample Salvia officinalis L. (essential oil described in ISO 9909:1997(E)), and Spanish sage (Salvia lavandulifolia) for example Salvialavandulifolia Vahl (essential oil described in ISO 3526:2005(E)).

Salvia extract is known to contain at least 4 active compounds. Atypical chromatographic profile for Salvia officinalis L. showsα-pinene, camphene, limonene, 1,8-cineole, α-thujone, β-thujone,camphor, linalol and linalyl acetate, bornyl acetate and α-humulene. Atypical chromatographic profile for Salvia lavandulifolia Vahl showsα-pinene, sabinene, limonene, 1,8-cineole, linalool, camphor, borneol,terpinen-4-ol, linalyl acetate, α-terpinyl acetate and sabinyl acetate.

Salvia extracts are commercially available.

The term “carvacrol” as used herein refers to2-methyl-5(1-methylethyl)-phenol (CAS 499-75-2). This compound can beobtained from oregano (Origanum vulgare) and other plants. A natureidentical compound can be synthesised and is commercially available.

As digestibility of lipid is believed to be improved by the invention,it is desirable to have a high lipid content in the feed so that fishgrowth is promoted as much as possible. Certain fish (includingsalmonids) require high lipid feed to remain healthy. Preferably, thefish feed contains at least 15 wt % lipid, more preferably at least 20wt % lipid, still more preferably at least 25 wt % lipid, for example,25 to 35 wt % lipid.

The fish feed preferably comprises carvacrol in an amount of 0.005-0.5wt % and/or salvia extract in an amount of at least 0.005-0.5 wt %. Morepreferably, the fish feed comprises carvacrol in an amount of 0.01-0.25wt % and/or salvia extract in an amount of 0.01-0.25 wt %. Suitably, thefish feed comprises carvacrol in an amount of 0.01-0.05 wt %, forexample 0.02-0.04 wt %, and/or salvia extract in an amount of about0.01-0.05 wt %, for example 0.02-0.04 wt %.

Preferably, the fish feed has a proximate composition of 30-50 wt %protein, 3-15 wt % moisture and lipid as described above.

Preferably, the fish feed comprises one or more of:

-   -   sources of protein, carbohydrate and lipid (for example, fish        meal, fish oil, animal meal (for example blood meal, feather        meal, poultry meal, chicken meal and/or other types of meal        produced from other slaughterhouse waste), animal fat (for        example poultry oil), vegetable meal (e.g. soya meal, lupin        meal, pea meal, bean meal, rape meal and/or sunflower meal),        vegetable oil (e.g. rapeseed oil, soya oil), gluten (e.g. wheat        gluten or corn gluten) and added amino acids (e.g. lysine));    -   vitamin premix;    -   mineral premix; and    -   pigment (e.g. canthaxanthin, astaxanthin).

In a second aspect, the invention relates to a method of making a fishfeed as described above.

Preferably, the method comprises the steps of:

-   -   mixing ingredients in a mixer;    -   extrusion or pressing of pellets; and    -   coating the pellets with oil.

The carvacrol and/or salvia extract is suitably either added to themixer or included in the coating oil.

Suitably, carvacrol is provided in the form of a mixture of carvacrolwith a dry carrier such as silica (for example a 50:50 mixture byweight), or in the form of pure carvacrol.

Similarly, salvia extract is suitably provided in the form of a mixtureof salvia extract with a dry carrier such as silica (for example a 50:50mixture by weight), or in the form of pure salvia extract.

In a third aspect, the invention relates to use of a fish feed asdescribed above for feeding fish. The feed is particularly suitable forfeeding salmonids, including Atlantic salmon (Salmo salar), other salmonspecies and trout, and non-salmonids such as cod, sea bass, sea breamand eel. However, it can be fed to all types of fish, for exampleturbot, halibut, yellow tail, saithe, and tuna.

In a fourth aspect, the invention relates to a fish fed with a fish feedas described above.

In a fifth aspect, the invention relates to use of carvacrol and/orsalvia extract for promoting growth of fish.

In a sixth aspect, the invention relates to use of carvacrol and/orsalvia extract for improving lipid digestibility in fish.

Features described in relation to any aspect of the invention may beused in any other aspect of the invention.

The invention will be further described with reference to thenon-limiting Examples.

General Method for Preparation of Pressed Fish Feed

The main raw materials are ground and mixed. Microingredients are addedto the mixer. The homogenous mix is conditioned by adding water andsteam to the mass in a preconditioner. This starts a cooking process inthe starch fraction (the binding component). The mass is fed into apellet mill. The mass is forced through the mill's die and the stringsare broken into pellets on the outside of the die. The moisture contentis low and drying of the feed is not necessary. Additional oil may besprayed onto the surface of pellets, but as the pellets are rathercompact, the total lipid content rarely exceeds 24%. The added oil maybe fish oil or vegetable oils, for example rape seed oil or soy oil, ora mixture of vegetable oils or a mixture of fish oil and vegetable oils.After oil coating, the pellets are cooled in a cooler and bagged.

General Method for Preparation of Extruded Fish Feed

The main raw materials are ground and mixed. Micro ingredients are addedto the mixer. The homogenous mix is conditioned by adding water andsteam to the mass in a preconditioner. Additional oil may also be addedto the mass at this stage. This starts a cooking process in the starchfraction (the binding component). The mass is fed into an extruder. Theextruder may be of the single screw or the twin-screw type. Due to therotational movement of the mass in the extruder, the mass is furthermixed. Additional oil, water and steam may be added to the mass in theextruder. At the end of the extruder, the mass has a temperature above100° C. and a pressure above ambient pressure. The mass is forcedthrough the openings in the extruder's die plate. Due to the relief intemperature and pressure, some of the moisture will evaporateimmediately (flash off) and the extruded mass becomes porous. Thestrings are cut into pellets by a rotating knife. The water content israther high (18-28%) and the pellets are therefore immediately dried toapproximately 10% water content in a dryer. After the dryer, more oilmay be added to the feed by spraying oil onto the surface of the feed,or by dipping the feed in oil. It is advantageous to add the oil to thefeed in a closed vessel where the air pressure is below ambient (vacuumcoating) so that the porous feed pellets absorb more oil. Feedcontaining more than 40% lipid may be produced this way. After thecoater, the feed is cooled and bagged. Oil may be added at severalplaces in the process as explained above, and may be fish oil orvegetable oils, by example rape seed oil or soy oil, or a mixture ofvegetable oils or a mixture of fish oil and vegetable oils.

EXAMPLE 1

The feeds used in Example 1 had a proximate composition of protein(45.6-47.4 wt %), lipid (30.2-32.2 wt %), moisture (5.2-6.2 wt %) andash (5.4-5.8 wt %),

A control feed was prepared from fish meal (407.4 g), soybean meal (55.8g), corn gluten (196.1 g), wheat (88.0 g), fish oil (247.3 g), mineraland vitamin premixes (3.8 g), yttrium premix (1.0 g, used to measurelipid digestibility as discussed below) and astaxanthin preparation (0.6g). Pellets were extruded using the process explained above and coatedwith the fish oil.

Test feeds containing 0.1 wt % and 0.2 wt % carvacrol formulation(containing 50 wt % carvacrol and 50 wt % silica carrier) were prepared.The amount of active substance was 500 and 1000 mg per kg feed,respectively. In the comparison feeds, the amount of wheat was reducedto 87.0 g and 86.0 g respectively. The carvacrol formulation was addedwith the other microingredients to the mixer before preconditioning.

Pellet size was 4 mm.

Test feeds containing 0.1 wt % and 0.2 wt % formulation of Salviaofficinalis salvia extract (containing 50 wt % salvia extract and 50 wt% silica carrier) were prepared in a similar way.

The feed was fed to Atlantic salmon (Salmo salar) weighing 169 g (±3 g)at the onset of the study. The fish was stocked in tanks (1 m×1 m).There were 30 fish in each tank. Sea water temperature was 11.8° C.(±0.5° C.). The fish were fed for 67 days. The study was run intriplicate.

The results are shown in Table 1.

TABLE 1 Feed Initial Final Specific conversion Feed weight (g) weight(g) growth rate ratio Control 170 ± 2.77 330 ± 13 0.99 ± 0.08 0.91 ±0.05 Carvacrol 169 ± 3.54 339 ± 18 1.04 ± 0.05 0.91 ± 0.05 0.05 wt %Carvacrol 171 ± 0.63 354 ± 6  1.09 ± 0.03 0.87 ± 0.03 0.1 wt % Salvia0.05 wt % 170 ± 2.89 339 ± 5  1.03 ± 0.03 0.88 ± 0.03 Salvia 0.1 wt %171 ± 1.18 354 ± 11 1.09 ± 0.04 0.83 ± 0.04

It can be seen that increasing amounts of carvacrol and increasingamounts of salvia extract each lead to increased fish growth andimproved feed utilisation.

EXAMPLE 2

The feeds used in Example 2 had a proximate composition of protein(46.0-46.9 wt %), lipid (30.8-31.9 wt %), moisture (4.9-5.6 wt %) andash (7.4-7.7 wt %).

Control and comparison feeds were prepared as in Example 1. Salvialavandulifolia salvia extract (CAS 8016-65-7) was used.

Pellet size was 4 mm.

The feed was fed to Atlantic salmon (Salmo salar) weighing 199 g (±2.4g) at the onset of the study. The fish were stocked in tanks (1 m×1 m).There were 35 fish in each tank. Sea water temperature was 12° C. Thefish were fed for 82 days. The study was run in triplicate.

The results are shown in Table 2 (SE stands for “standard error”).

TABLE 2 Initial Final Specific Feed conver- weight weight growth ratesion ratio Feed (g) SE (g) SE SE SE Control 198 0.95 488 5.50 1.10 0.080.74 0.03 Carvacrol 199 1.29 512 6.81 1.16 0.01 0.68 0.02 0.05 wt %Carvacrol 200 1.19 503 6.89 1.13 0.01 0.70 0.01 0.1 wt % Salvia 0.05 1991.23 490 6.18 1.10 0.01 0.73 0.00 wt % Salvia 0.1 198 1.18 505 6.57 1.150.02 0.70 0.02 wtIt can be seen that increasing amounts of carvacrol and increasingamounts of salvia extract each lead to increased fish growth andimproved feed utilisation.

Lipid digestibility was determined using a standard method and theresults are shown in Table 3.

TABLE 3 ADC (%) lipid Feed (%) SE Control 96.39 0.35 Carvacrol 95.780.07 0.05 wt % Carvacrol 97.65 0.02 0.1 wt % Salvia 0.05 wt % 98.19 0.16Salvia 0.1 wt % 98.20 0.19

It can be seen that increasing amounts of carvacrol and increasingamounts of salvia extract each lead to increased lipid digestibility.Lipid digestibility for the groups fed salvia extract at the 0.05 wt %as well as the 0.1 wt % level were significantly higher than for thecontrol group.

EXAMPLE 3

The feeds used in Example 3 had a proximate composition of protein(44.3-46.2 wt %), lipid (28.2-31.4 wt %) and moisture (6.0-6.5 wt %).

Control feed was prepared from South-American fish meal (526.2 g),soybean meal (40.0 g), corn gluten (79.0 g), wheat (120.4 g),South-American fish oil (230.3 g), mineral and vitamin premixes (2.5 g),yttrium premix (1.0 g), and astaxanthin preparation (0.6 g). Pelletswere extruded using the process explained above and coated with the fishoil.

Test feeds were prepared containing carvacrol and/or salvia extract(Salvia lavandulifolia). Carvacrol and/or salvia extract were each addedas 100% oil. Two different inclusion levels of separate carvacrol andsalvia extract (0.5 g/kg and 1.0 g/kg) were tested.

Two test feeds were prepared with a combination of carvacrol and salviaextract. The inclusion levels were 1.0 g carvacrol and 0.2 g/kg salviaextract, and 0.5 g/kg carvacrol and 0.5 g/kg salvia extract,respectively. The carvacrol oil and/or salvia extract was mixed with thefish oil and coated onto the surface of the pellets by vacuum coatingafter drying of the pellets.

Pellet size was 3 mm for all feeds.

The feed was fed to Atlantic salmon (Salmo salar) weighing 156 g (±13 g)at the onset of the study. The fish was stocked in tanks holding 100 Lwater. There were 25 fish in each tank. Sea water temperature was 8.9°C.±0.2° C. The fish were fed for 96 days. The study was run with fourcontrol groups and one tank each for the different inclusion levels ofcarvacrol, salvia extract or combined carvacrol and salvia.

Apparent digestibility was determined for protein, the saturated fattyacid C16:0, the sum of all saturated fatty acids and the total lipid.The results are shown in Table 4.

TABLE 4 ADC ADC ADC protein C16:0 saturated (%) (%) fatty ADC total Feed(g) (g) acids (%) lipid (%) Control 86.8 69.2 69.8 87.8 Carvacrol 88.875.3 75.5 89.2 0.05 wt % Carvacrol 87.6 74.0 74.4 89.2 0.10 wt % Salvia0.05% 87.7 73.0 73.1 89.1 Salvia 0.10 wt % 88.8 76.9 77.0 90.6 Carvacrol86.8 75.1 75.3 89.9 0.10 wt %/ Salvia 0.02 wt % Carvacrol 87.8 75.3 75.689.4 0.05 wt %/ Salvia 0.05 wt %

It can be seen that increasing amounts of carvacrol and increasingamounts of salvia extract each lead to increased lipid digestibility andprotein digestibility.

It will be appreciated that, although the invention has been describedwith reference to examples, various modifications are possible withinthe scope of the invention.

The invention claimed is:
 1. A fish feed comprising carvacrol, wherein alipid content of the fish feed is at least 25 wt %, and wherein the fishfeed is an extruded or pressed pellet.
 2. The fish feed of claim 1,comprising 25-35 wt % of lipids.
 3. The fish feed of claim 1, comprising0.005-0.5 wt % of carvacrol.
 4. The fish feed of claim 3, comprising0.01-0.25 wt % of carvacrol.
 5. The fish feed of claim 4, comprising0.01-0.05 wt % of carvacrol.
 6. The fish feed of claim 1, wherein thecarvacrol is synthetic or is extracted from Origanum vulgare.
 7. Thefish feed of claim 1, further comprising 0.005-0.5 wt % of a Salviaessential oil.
 8. The fish feed of claim 7, wherein said Salviaessential oil is selected from a) Salvia officinalis L. essential oilcomprising α-thujone, β-thujone, camphor, linalool, linalyl acetate,bornyl acetate and α-humulene or b) Salvia lavandulifolia essential oilcomprising α-pinene, sabinene, limonene, 1,8-cineole, linalool, camphor,bomeol, terpine-4-ol, linalyl acetate, α-terpinyl acetate and sabinylacetate.
 9. The fish feed of claim 8, wherein the Salvia essential oilis Salvia lavandulifolia extract CAS 8016-65-7.
 10. The fish feed ofclaim 1, further comprising 30-50 wt % of protein; 3-15 wt % ofmoisture, and 0.005-0.5 wt % of carvacrol.
 11. The fish feed of claim 1,further comprising 30-50 wt % of protein.
 12. A fish feed comprisingcarvacrol, lipids, protein and moisture, wherein a lipid content of thefish feed is at least 25 wt %.
 13. The fish feed of claim 12, comprising25-35 wt % of lipids.
 14. The fish feed of claim 13, comprising 30-50 wt% of protein.
 15. The fish feed of claim 12, comprising 0.01-0.25 wt %of carvacrol.
 16. The fish feed of claim 15, comprising 0.01-0.05 wt %of carvacrol.
 17. The fish feed of claim 12, comprising 0.005-0.5 wt %of carvacrol.
 18. The fish feed of claim 12, wherein the carvacrol issynthetic or is extracted from Origanum vulgare.
 19. The fish feed ofclaim 12, further comprising 0.005-0.5 wt % of a Salvia essential oil.20. The fish feed of claim 19, wherein said Salvia essential oil isselected from a) Salvia officinalis L. essential oil comprisingα-thujone, β-thujone, camphor, linalool, linalyl acetate, bornyl acetateand α-humulene or b) Salvia lavandulifolia essential oil comprisingα-pinene, sabinene, limonene, 1,8-cineole, linalool, camphor, bomeol,terpine-4-ol, linalyl acetate, α-terpinyl acetate and sabinyl acetate.21. The fish feed of claim 20, wherein the Salvia essential oil isSalvia lavandulifolia extract CAS 8016-65-7.
 22. The fish feed of claim12, wherein the fish feed is an extruded or pressed pellet.
 23. A methodcomprising feeding fish with a fish feed comprising carvacrol, wherein alipid content of the fish feed is at least 25 wt %, and wherein the fishfeed is an extruded or pressed pellet.
 24. The method of claim 23,wherein the fed fish are salmonids.